On 08/31/2013 04:49 AM, Bob Stewart wrote: > Hi Bob, > > You've given me a lot to work with. Perhaps the best answer is to put in a > user parameter for how many seconds between updates to consider a lock > condition. For warmup, I had planned to put in a 5 minute holdover period, > but that could easily be user configurable, as well. The point about referring to "within 45 degrees" is that you will not see any remaining cycle slips for sure (well, unless you have a very bumpy ride). The actual decision point lies earlier if you look at it theoretical, but this is a handy one. In that context, you can select any other arbitrary handy limit which fits your needs as long as you are on the safe side.
Saying within X ns and X is sufficiently low you are actually saying "I am locked in, oscillator frequency well within limits and it will keep pulling in and now I also is within phase/time deviations fitting my needs". Then, if your goal is only to produce frequency, then the time-limit can be a bit strange, but for a PLL it is natural as it is Phase Locked loop. The remaining phase error continue to decay at the time-constant of the loop, until the oscillators drift and temperature dependence dominates (there can be other environmental changes too). In fact, you can expect the oscillator to move around a little and hence require updates, so an up-date rate thing needs to be well above that background regulation need, whatever that is. DAC values keep changing even if ever so slowly. There is also noise in the frequency reading, which needs to be compensated by the loop, so that will be exposed in the frequency reading. So, for long term aspect, the time error is a good and relatively straight-forward measure to use. Cheers, Magnus _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
